1. Field of the Invention
The present invention relates to a sanitary napkin having a three-dimensional structure intended to come into contact with at least one of the vagina and the intergluteal cleft, which extends posteriorly from the anus of the wearer's body, and more particularly to a sanitary napkin whose napkin body can be easily kept curved to conform to the contour of the wearer's body while the three-dimensional structure is kept in contact with the wearer's body.
2. Description of the Related Art
Conventional sanitary napkins include ones having a protruding structure, which is intended to come into close contact with the wearer's body, on a skin-side surface of a napkin body containing a liquid absorbent layer.
Patent Publication 1 identified below discloses a sanitary napkin in which a longitudinally extending elastic member is provided between a liquid absorbent layer and a topsheet covering the skin-side surface of the liquid absorbent layer. The elastic member exhibits an elastic contractive force to bring front and rear edges of the sanitary napkin closer to each other, so that the sanitary napkin is curved to have its skin-side surface recessed and also the center of the topsheet is lifted away from the liquid absorbent layer because of the elastic member. By keeping the topsheet thus lifted away from the liquid absorbent layer in close contact with the wearer's body, menstrual blood is allowed to be absorbed by the liquid absorbent layer via the topsheet.
Patent Publication 2 identified below discloses a sanitary napkin in which a three-dimensional structure, which is formed of a liquid-permeable sheet to have a T-shaped cross-section, is provided on the skin-side surface of a napkin body. The three-dimensional structure is provided with elastic members for exhibiting a longitudinal contractive force. These elastic members exert a force to bring front and rear edges of the napkin body closer to each other so that the napkin body is curved, which makes the three-dimensional structure rise from the skin-side surface of the napkin body. This three-dimensional structure can be kept in close contact with the female genital organ and is aimed at providing a pleasant feeling during wear.
Patent Publication 3 identified below discloses a sanitary napkin including a primary absorbent member of a triangular cross-section. This primary absorbent member is composed of an absorbent core for absorption and retention of liquid and an outer cover covering the absorbent core. In this sanitary napkin disclosed in Patent Publication 1, the primary absorbent member comes into close contact with the vaginal opening so that menstrual blood can be mainly absorbed and retained by the primary absorbent member. The sanitary napkin also includes a secondary absorbent member which is flat and intended to come into contact with garments and the primary absorbent member is disposed on the secondary absorbent member.
Patent Publication 4 identified below discloses a sanitary napkin including a tube of absorbent material having a function of absorbing liquid. This tube of absorbent material is composed of an absorbent material shaped into a tube and a cover covering the absorbent material and therefore the tube of absorbent material is allowed to comfortably fit to the vaginal opening of a wearer. Here, the tube of absorbent material is disposed on a base pad.
Patent Publication 5 identified below discloses a hump of a triangular cross-section bulging from a skin-side surface of a sanitary napkin. This hump is composed of an absorbent body and a stiffening element disposed between a liquid-permeable topsheet and a liquid absorbent layer, and the stiffening element is formed of a rigid material such as a plastic sheet. Even when the hump reinforced by the stiffening element comes into contact with the vaginal opening and is subjected to a compressive force due to body pressure, the hump can keep the sanitary napkin in close contact with the vaginal opening without being crushed down.
Patent Publication 6 identified below discloses a sanitary napkin having a heaped protrusion in a rear region of a skin-side surface. From the description of Patent Publication 4, it is unclear how the protrusion is constituted, but it describes that the protrusion comes into contact with the cleft of the buttocks to prevent rearward leakage of menstrual blood.    Patent Publication 1: Japanese Unexamined Patent Publication No. 2000-83994    Patent Publication 2: Japanese Unexamined Patent Publication No. 2002-320638    Patent Publication 3: Japanese Unexamined Patent Publication No. H11-500940    Patent Publication 4: Japanese Unexamined Patent Publication No. 2002-512851    Patent Publication 5: Japanese Unexamined Patent Publication No. 2001-504727    Patent Publication 6: Japanese Unexamined Patent Publication No. H11-42250
In either of the sanitary napkins disclosed in Patent Publications 1 and 2, the three-dimensional structure is formed to bulge from the skin-side surface of the napkin body for coming into contact with the vaginal opening, but the sheet forming the three-dimensional structure does not have a sufficient stiffness in itself to maintain the shape of the three-dimensional structure. The three-dimensional structure is kept bulging by string-like elastic members that exhibit an elastic contractive force in the longitudinal direction.
Accordingly, when the three-dimensional structure is in contact with the vaginal opening, a wearer may sense a local pressure due to tension of the elastic members to cause an unpleasant feeling. Therefore, it is necessarily required to set the tension of the elastic members to a relatively low level. Since the three-dimensional structure in which the tension of the elastic members is set to a relatively low level tends to come into soft contact with the wearer's body, it is suitable for coming into close contact with the vaginal opening, but does not have a sufficient stiffness to enable intrusion into the intergluteal cleft, which extend posteriorly from the anus. Hence, the three-dimensional structure cannot be brought into close contact with the intergluteal cleft and becomes less effective in preventing menstrual blood from flowing down the intergluteal cleft posteriorly during sleep.
In the sanitary napkins disclosed in Patent Publications 3 to 5, on the other hand, the three-dimensional structure disposed on the skin-side surface of the napkin body has the absorbent. In the sanitary napkins where the absorbent is disposed on the skin-side surface of the napkin body, however, when the napkin body is curved to fit the wearer's body from the crotch to the buttocks, the three-dimensional structure is longitudinally contracted to exhibit a repulsive force against compression. Accordingly, the sanitary napkin worn on the wearer's body tries to recover to its original flat shape, which easily creates a clearance between the skin-side surface of the napkin body and the wearer's body.
Particularly in the sanitary napkin disclosed in Patent Publication 5, since the three-dimensional structure contains the rigid material such as a plastic sheet, the rigid material interferes with the curvature of the napkin body. In addition, a wearer tends to feel uncomfortable when the rigid material comes into contact with the wearer's body.
In the sanitary napkin disclosed in Patent Publication 6, on the other hand, although the structure of the protrusion is unclear, the protrusion appears to function to interfere with the curvature of the napkin body in the same manner as those disclosed in Patent Publications 3 to 5.